Carbonaceous fuels, such as coal and coal char, generally contain sulfur and produce sulfur dioxide upon combustion, an objectionable air pollutant. The presence of sulfur in carbonaceous fuels is further objectionable because of governmental air purity standards which restrict the use of fuels to those containing relatively low concentrations of sulfur. The need for relatively sulfur-free carbonaceous fuels is therefore very important, especially in view of dwindling supplies of oil and natural gas and abundant supplies of coal and other carbonaceous materials which may be utilized as a fuel.
Carbonaceous fuels may be desulfurized by treatment with hot, molten caustic materials such as sodium hydroxide, potassium hydroxide, and the like. Aqueous solutions of caustic materials may also be employed to desulfurize carbonaceous fuels but the degree of desulfurization is not nearly as great as when a hot melt of the caustic materials is employed.